Seismic surveys are carried out on a wide scale throughout the world primarily for defining underground formations to detect and localize petroleum deposits. In past years the primary source of seismic energy for such surveys has been explosives, such as dynamite. However, the current dominant energy source for land seismic exploration is a seismic vibrator. The use of such a vibrator is generally identified by the trademark VIBROSEIS.
The conventional method for collecting seismic records by the use of a vibrator source is to lay out a line or multiple lines of detector geophones and sequentially operate the vibrator source along a series of points on a line of travel. The seismic geophone array and the vibrator is then offset to a different line to collect more information. The cost for producing a seismic survey is closely related to the amount of time required to operate the vibrator, collect the seismic records and move the detector geophones. A primary limiting feature in the speed of collecting seismic data is the use of only a single vibrator source.
In a proposal by R. Garotta entitled "Simultaneous Recording of Several Vibroseis Seismic Lines" (S5.5) presented at the 53rd Annual International Meeting and Exposition of the Society of Exploration Geologists in 1983, it is suggested that vibrators could be operated along parallel lines with either sequential or simultaneous recording. However, the technique proposed by Garotta is severely limited since it provides incomplete separation of sources.
It would be a more economical approach to the collecting of seismic data if there could be simultaneous use of a plurality of vibrator sources. However, the signals from the various vibrator sources would be mixed. Harmonic distortion produced by each of the sources would also be mixed. Therefore, there exists a need for a method for producing separate seismic records which are derived from a plurality of simultaneously operated vibrator seismic sources. Such a method could serve to substantially reduce the cost of producing seismic surveys.